Themes
The first qualification in a general is a cool head – that is, a head which receives accurate impressions, and estimates things and objects at their real value. He must not allow himself to be elated by good news, or depressed by bad.
— Napoleon Bonaparte

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
Napoleon says a general's first asset is a steady mind that sees things as they are. Good news shouldn't thrill him and bad news shouldn't crush him. It's a view of command as calm, accurate judgment over emotion.
Context reviewed